Image processing apparatus

Abstract

An image processing apparatus comprises a set of infra-red (IR) sources surrounding an image capture sensor and a processor operatively coupled to said IR sources and said image capture sensor. The processor being arranged to acquire from the sensor a succession of images, each illuminated with a different combination of the IR sources. The processor is further arranged to combine component images corresponding to the succession of images by selecting a median value for corresponding pixel locations of the component images as a pixel value for the combined image.

The invention claimed is: 
     
       1. An image processing apparatus comprising:
 an image capture sensor; 
 a set of infra-red (IR) sources surrounding the image capture sensor; and 
 a processor operatively coupled to said IR sources and said image capture sensor and configured to acquire from the sensor a succession of images, each image illuminated with a different combination of the IR sources such that each in a plurality of the images is captured with illumination from a different direction, the processor being further arranged to combine component images corresponding to the succession of images by selecting a median value for corresponding pixel locations of said component images as a pixel value for the combined image, where the processor arranged to perform 3D temporal median filtering in a cascaded fashion to obtain g sets of cascaded images which are passed through a median filter with g intermediate fused images generated and combined into said combined image. 
 
     
     
       2. An image processing apparatus as claimed in  claim 1  wherein said processor is arranged to acquire each of said succession of images with a high-pass filter to compensate for an illumination gradient across said succession of images from respective illuminating light sources. 
     
     
       3. An image processing apparatus as claimed in  claim 2  wherein said processor is further arranged to normalise said images processed with said high-pass filter so that pixel values of said component images are in the range [0,1]. 
     
     
       4. An image processing apparatus as claimed in  claim 1  wherein said processor is further arranged to apply a Gabor filter bank to said combined image to provide a finger vein map. 
     
     
       5. An image processing apparatus as claimed in  claim 1  wherein said processor comprises a processor for a consumer electronic device. 
     
     
       6. An image processing apparatus as claimed in  claim 1  wherein said processor comprises at least one dedicated processing module within a consumer electronic device. 
     
     
       7. An image processing apparatus as claimed in  claim 1  wherein said apparatus comprises 12>N>6 light sources. 
     
     
       8. The image processing apparatus of  claim 7  wherein said processor is configured to capture a succession of N images, each lit by one or more different light sources. 
     
     
       9. An image processing apparatus as claimed in  claim 1  wherein said processor is further arranged to spatially align said succession of images. 
     
     
       10. An image processing apparatus as claimed in  claim 1  wherein each light source comprises an NIR LED. 
     
     
       11. An image processing apparatus as claimed in  claim 1  further comprising an image store for at least temporarily storing said succession of images and/or said combined image. 
     
     
       12. An image processing apparatus as claimed in  claim 1  wherein the processor is further arranged to combine respective sets of component images corresponding to plural sets of acquired images by selecting a median value for corresponding pixel locations of said component images as a pixel value for a respective intermediate combined image, the processor being arranged to combine said intermediate combined images by selecting a median value for corresponding pixel locations of said intermediate combined images as a pixel value for a final combined image. 
     
     
       13. A consumer electronic device incorporating the image processing apparatus according to  claim 1  and being arranged to employ said image processing apparatus to register a user with an application and/or said device and to authenticate a user to an application and/or said device. 
     
     
       14. The image processing apparatus of  claim 4  where said processor is further arranged to apply the Gabor filter bank to a fused finger vein image for I different directions, applying the 3D temporal median filter to I different images, and repeating the foregoing steps for p different frequencies. 
     
     
       15. The image processing apparatus of  claim 14  where I=24. 
     
     
       16. The image processing apparatus of  claim 14  where p=5. 
     
     
       17. The image processing apparatus of  claim 16  where the different frequencies are 0.0250 Hz, 0.0270 Hz, 0.0290 Hz, 0.0310 Hz and 0.0330 Hz.